Tube pump

ABSTRACT

A tube pump comprising a tube formed beforehand into a shape adapted for the inner circumferential face of the housing. With this configuration, the tube can be used without problems even when the inner circumferential face of the housing is small and when the curvature of the inner circumferential face is large, and squeezing can be carried out by applying a small pressure force to the tube. Hence, the size of the pump is prevented from being made larger, and breakage of the tube owing to repeated deformations does not occur because the amount of deformation of the tube is reduced. Furthermore, synthetic resins having high chemical resistance can be used as materials of the tube. Hence, unlike a rubber tube, the tube of the present invention is suited for a wide range of applications.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a tube pump, more particularlyto an improvement of a tube for use in the tube pump.

[0003] 2. Description of the Prior Art

[0004] A tube pump is configured such that a tube is disposed in a ringshape along a circular inner circumferential face formed in a housingand such that the tube is squeezed sequentially in the longitudinaldirection thereof by a pressure application member disposed inward, suchas a roller or a ring, so as to feed fluid from the inside of the tube.A straight tube, which is made of a rubber elastic material, circular ornearly circular in cross section and stretchable and compressible inboth the radial and longitudinal directions, is generally used as a tubefor this pump. This tube is bent in a ring shape and disposed along theinner circumferential face of the housing.

[0005] When the straight tube is bent during use as described above, theouter side of the bent tube is stretched, and the inner side thereof iscompressed. Hence, if the curvature of the bent tube exceeds a certainlimit, the tube results in buckling, and the buckling portion becomesflat, whereby the effective cross-sectional area of the tube becomessmall and the pump cannot deliver its intended capacity. To prevent thisproblem, it is necessary to take countermeasures. For example, thediameter of the inner circumferential face of the housing is made largerto decrease the curvature thereof, or the wall thickness of the tube ismade larger to make the tube resistant to flattening. However, thesecountermeasures become great factors making the size of the pump larger.

[0006] In addition, in order to operate the pump efficiently, the tubeis required to be flattened completely so as not to cause any clearanceinside when the tube is squeezed, and also required to return to itsoriginal shape promptly after squeezing. However, in the case of a tubebeing circular in cross section, in order to completely flatten thistube, it is necessary to apply a pressure force that is large enough tofold back the wall of the tube 180 degrees at both ends thereof in crosssection. Furthermore, in order to allow the tube to return to itsoriginal shape promptly after squeezing, it is preferable that theelastic force of the tube is larger. Hence, it is necessary that thepressure force is large enough to cope with this large elastic force.Therefore, these also become great factors making the size of the pumplarger. Moreover, these require extra energy significantly exceedingenergy required for fluid transfer. As a result, the efficiency of thepump is lowered, and the tube is apt to break at portions whereinfolding back is repeated, thereby increasing maintenance cost.

[0007] Still further, since a freely stretchable and compressible tubehaving rubber-like elasticity is required, the material of the tube thatcan be used for the pump is limited. Hence, it is impossible to usetubes made of synthetic resins having high chemical resistance, such aspolypropylene, polyethylene and fluorocarbon resin, thereby causing aproblem of limiting the application range of the pump.

SUMMARY OF THE INVENTION

[0008] In view of these problems, a first object of the presentinvention is to provide a compact tube pump. A second object of thepresent invention is to reduce energy required for pump operation. Athird object of the present invention is to provide a tube pumpcomprising a tube being resistant to breakage. Furthermore, a fourthobject of the present invention is to provide a tube pump having veryfew limitations on the material of the tube so as to be usable for wideapplications.

[0009] In order to attain the above-mentioned objects, the tube pump ofthe present invention uses a tube formed beforehand into a shape adaptedfor the inner circumferential face of the housing.

[0010] The specific configuration of the tube pump of the presentinvention, more particularly the specific configuration of its tube,will become apparent from the following descriptions of embodiments ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a schematic front view showing an embodiment of a tubepump in accordance of the present invention;

[0012]FIG. 2A is a perspective view showing a tube for use in the pump;

[0013]FIG. 2B is a sectional view showing a shape of the squeezedportion of the tube;

[0014]FIG. 3A is a sectional view showing another shape of the squeezedportion of the tube;

[0015]FIG. 3B is a sectional view showing still another shape of thesqueezed portion of the tube;

[0016]FIG. 4 is a sectional view showing shapes of the pressureapplication faces of the pump and a further shape of the squeezedportion of the tube;

[0017]FIG. 5A is a sectional view showing a still further shape of thesqueezed portion of the tube for use in the pump; and

[0018]FIG. 5B is a sectional view showing a squeezed condition of thestill further shape of the squeezed portion of the tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Referring to FIG. 1, numeral 1 designates a housing having aninner circumferential face 2. On the inner circumferential face 2, acircular pressure application face 2 a is formed in a range larger thanthe half and smaller than the whole of the circumference of the innercircumferential face 2. An opening portion 2 b is provided at a portionwherein the pressure application face 2 a is not formed. Numeral 3designates a tube. The tube 3 is disposed along the innercircumferential face 2. The straight extension portions 3 a at both endsof the tube 3 are extended outside the housing 1 from the openingportion 2 b.

[0020] Numeral 4 designates a ring-shaped pressure application memberdisposed on the inner side of the tube 3. The pressure applicationmember 4 has a double structure comprising an inner ring 41 and an outerring 42. The inner ring 41 is made of a rigid material having a lowfriction coefficient, such as a fluorocarbon-resin-based synthetic resinmold. The outer ring 42 is formed of a mold made of an elastic materialhaving a high friction coefficient, such as rubber. The outercircumference of the outer ring 42 is used as a pressure applicationface 4 b.

[0021] Numeral 5 designates an eccentric driving member disposed on theinner side of the pressure application member 4. Numeral 6 designates arotation shaft on which the eccentric driving member 5 is installed. Theeccentric driving member 5 rotates for example clockwise as seen in FIG.1 while its circular outer circumferential face 5 a makes slidingcontact with the inner circumferential face 4 a of the pressureapplication member 4. Hence, the pressure application member 4 carriesout circular motion along the inner circumferential face 2 of thehousing 1, whereby the pressure application faces 2 a and 4 b hold thetube 3 therebetween and squeeze the tube 3 sequentially toward the leftextension portion 3 a as seen in FIG. 1. A drive motor (not shown) isdisposed on the rear face of the housing 1, and the output shaft of themotor is directly used as the rotation shaft 6 or connected to therotation shaft 6 via an appropriate reduction gear.

[0022] The tube 3 is formed of a synthetic resin mold having a highchemical resistance, such as polypropylene, polyethylene andfluorocarbon resin. As a whole, the tube 3 has a shape shown in FIG. 2A.The straight extension portion 3 a adapted for the opening 2 b is formedat each end of the ring-shaped squeezed portion 3 c adapted for thepressure application face 2 a of the housing 1 so as to be integratedwith the squeezed portion 3 c. In addition, a connection portion 3 b forconnection to another apparatus via a tube is formed at the end of theextension portions 3 a. The connection portion 3 b is provided withappropriate annular projections to prevent disconnection. This tube 3 isnot so flexible as rubber because it is a mold made of theabove-mentioned material. Furthermore, the tube 3 has some hardness andrigidity, and also has elasticity so as to be deformable and so as toreturn to its original shape after deformation. The shape of the tube 3shown in FIG. 2A is just an example, and it is needless to say that thetube 3 can be formed into a shape adapted for the inner circumferentialface 2 of the housing 1 in which the tube 3 is used.

[0023]FIG. 2B is a sectional view taken along a plane in a directionperpendicular to the length of the squeezed portion 3 c. In other words,its cross section has a flat shape wherein an outer side 3 d makingcontact with the housing 1 is joined to an inner side 3 e making contactwith the pressure application member 4 at joint portions 3 f. An angle Aat which the outer side 3 d intersects the inner side 3 e is an acuteangle. Both the outer side 3 d and the inner side 3 e have circular arcshapes slightly inflated outward. Since the squeezed portion 3 c isextended in the direction of flatness of the tube 3, the thickness ofthe outer side 3 d and the thickness of the inner side 3 e are farsmaller than that of the extension portion 3 a. In FIG. 2B, it isassumed that the cross sections of the outer side 3 d and the inner side3 e have ordinary circular arc shapes. However, the cross sections mayhave circular arc shapes partially taken from ellipses.

[0024] Since the tube pump 11 of this embodiment comprises the tube 3having the above-mentioned shape, the outer side 3 d and the inner side3 e having small wall thicknesses and slightly inflated shapes shouldonly be flattened at the time of squeezing. Since the angle at the jointportion 3 f is an acute angle, the amount of its deformation is small atthe time of squeezing. Furthermore, in the case of this deformation,both the ends are not folded back 180 degrees when flattened. Hence, theouter side 3 d and the inner side 3 e should only have elasticity to theextent that they can return to their inflated shapes. For this reason,the wall thicknesses of the outer side 3 d and the inner side 3 e can bemade smaller. Therefore, the tube can be squeezed completely by applyinga smaller pressure force in comparison with a case wherein a circularrubber tube is squeezed, and breakage at the joint portions 3 f owing torepeated deformations is less likely to occur. Still further, since thedeformations at the outer side 3 d and the inner side 3 e are small,they can return promptly to their original shapes after squeezing byvirtue of the recovery forces of the outer side 3 d, the inner side 3 eand the joint portions 3 f.

[0025]FIGS. 3A and 3B show examples of other sectional shapes of thesqueezed portion 3 c. The shapes of the outer side 3 d and the innerside 3 e shown in FIG. 3A are formed of broken lines wherein the outerside 3 d and the inner side 3 e are inflated and bent outward therebyforming a rhombus. In addition to this rhombus, it is possible to have aflat hexagon or the like. Furthermore, the shape shown in FIG. 3B issimilar to that shown in FIG. 2B, but the joint portions 3 f have finshapes extending in the direction of flatness of the tube 3. The outerside 3 d and the inner side 3 e have shapes smoothly inflated inparallel with the fin-shaped joint portions 3 f. Hence, deformations atthe joint portions 3 f are almost negligible, whereby the tube 3 can besqueezed easily to a flat shape. In this case, when the sum of the wallthickness of the outer side 3 d and the wall thickness of the inner side3 e is made equal to the wall thickness of the joint portion 3 f, andwhen the tube 3 is squeezed and flattened, the thickness of the tube 3becomes constant on the whole.

[0026] Since the tube 3 is formed into the shape adapted for the innercircumferential face 2 of the housing 1 beforehand as described above,even when the housing 1 is small and when the curvature of the innercircumferential face 2 is large, no extension force applies to the outerside of the curved shape of the tube 3, and no compression force appliesto the inner side of the curved shape of the tube 3 during pumpoperation. Furthermore, the sectional shape of the squeezed portion 3 cof the tube 3 that is squeezed during pump operation is a flat shapewherein the outer side 3 d on the side of the housing 1 and the innerside 3 e on the side of the pressure application member 4 are joined toeach other at acute angles. Hence, the wall thickness of the squeezedportion 3 c can be decreased, and the amount of its deformation at thetime of squeezing can be reduced, whereby squeezing can be carried outsecurely by applying a relatively small pressure force.

[0027] With these overall effects, the size of the pump is preventedfrom being made larger, and breakage of the tube owing to repeateddeformations does not occur because the amount of deformation of thetube is reduced. Furthermore, a variety of synthetic resins can be usedas materials of the tube, whereby it is possible to obtain a tube pumpapplicable to a variety of medicines and chemical products.

[0028] Still further, this kind of pump is not used independently, butis required to be connected between external apparatuses via connectiontubes in order to receive and deliver fluid to be transferred. In thisembodiment, the connection to the external apparatuses is easy, sincethe connection portion 3 b is formed at each end of the tube 3 so as tobe integrated therewith as described above.

[0029] In the embodiment, it is assumed that the pressure applicationface 2 a of the housing 1 and the pressure application face 4 b of thepressure application member 4 are cylindrical and that their sectionalshapes are straight in the axial direction. The squeezed portion 3 c ofthe tube 3 is symmetrical with respect to its centerline in thedirection of flatness of the tube 3.

[0030] On the other hand, as shown in FIG. 4, one of the pressureapplication face 2 a of the housing 1 and the pressure application face4 b of the pressure application member 4 can have a convex circular arcshape in cross section, and the other can have a concave circular arcshape in cross section adapted for the convex circular shape. In thiscase, it is preferable that the wall thickness of one of the outer side3 d and the inner side 3 e of the tube 3, making contact with theconcave pressure application face, is made larger, and that the wallthickness of the other, making contact with the convex pressureapplication face, is made smaller. In FIG. 4, the pressure applicationface 4 b is made convex, the pressure application face 2 a is madeconcave, the wall thickness of the outer side 3 d of the tube 3 is madelarger, and the wall thickness of the inner side 3 e is made smaller. Inthe case of this shape, the side that is thin and deformable easily atthe time of squeezing, that is, the inner side 3 e in the example shownin FIG. 4, can be deformed and pressed easily against the outer side 3 dwith no clearance therebetween as indicated in a chain line. Hence, nolarge pressure force is required for squeezing. Furthermore, aftersqueezing, the inner side 3 e returns to its original shape by virtue ofits elasticity.

[0031] Generally speaking, a thin object having a slightly inflatedshape has the property of being deflated abruptly because of a kind ofbuckling phenomenon when an external pressure larger than the deflationpressure of the object is applied to the object and returning to itsoriginal shape abruptly when the external pressure becomes extinct. Inthe case of this tube 3, by properly selecting the wall thickness andthe inflated shape of the inner side 3 e, the inner side 3 e can bedeflated easily by slight pressure application and can immediatelyreturn to its original shape when the pressure application ceases. Byusing this property, it is possible to obtain a tube wherein the innerside 3 e can make completely close contact with the outer side 3 d byapplying a small pressure force and the inner side 3 e returns promptlyto its original shape after squeezing. This so-called can-deflatingeffect can be obtained by properly selecting the wall thickness andinflated shape. Hence, an effect similar to this effect can also beobtained even when the wall thickness of the outer side 3 d is equal tothat of the inner side 3 e.

[0032]FIGS. 5A and 5B show an example wherein the shape returning forceof the tube 3 is improved by using a structure different from theabove-mentioned structures. In this example, at least the squeezedportion 3 c of the tube 3, a synthetic resin mold, is covered with arubber tube 8. It is preferable that this rubber tube 8 has a size thatachieves a slightly stretched condition when the tube 3 is covered withthe rubber tube 8. In this configuration, in a condition wherein thetube 3 is squeezed and flattened as shown in FIG. 5B, an inwardcontracting stress is produced in the stretched rubber tube 8 asindicated by the arrows. Hence, the returning force of the rubber tube 8is superimposed on the returning force of the tube 3 itself, whereby thetube 3 can promptly return to its original shape after squeezing.

[0033] Unlike the structure wherein the tube 3 is covered with therubber tube 8 shown in FIGS. 5A and 5B, for example, a structure, inwhich cushion members made of sponge or the like are disposed atpositions making contact with the connection portions 3 f at both endsof the tube 3 when squeezed and flattened, may be used. In other words,the forces for returning the connection portions 3 f are generated bythe cushion members. Even when this configuration is used, the tube 3can return promptly to its original shape after squeezing.

[0034] As a result, with the above-mentioned configurations, the tubecan return promptly to its original shape after the squeezing of thetube is completed, whereby it is possible to obtain an efficient tubepump.

What is claimed is:
 1. A tube pump comprising a tube disposed in a ringshape along a circular inner circumferential face formed in a housing,said tube being squeezed sequentially in the longitudinal directionthereof by a pressure application member disposed inward so as to feedfluid from the inside of said tube, wherein said tube is formedbeforehand into a shape adapted for said inner circumferential face ofsaid housing.
 2. A tube pump in accordance with claim 1, wherein saidtube is made of a synthetic resin, and the squeezed portion thereof isflat in cross section such that the outer side of said tube on the sideof said housing and the inner side of said tube on the side of saidpressure application member are joined to each other at acute angles. 3.A tube pump in accordance with claim 2, wherein the outer side and theinner side of said tube have circular arc shapes in cross section.
 4. Atube pump in accordance with claim 2, wherein the outer side and theinner side of said tube have broken line shapes in cross section.
 5. Atube pump in accordance with claim 3, wherein one of the pressureapplication face of said inner circumferential face of said housing andthe pressure application face of said pressure application member has aconvex circular arc shape and the other has a concave circular arc shapein cross section.
 6. A tube pump in accordance with claim 5, wherein thewall thickness of one of the outer side and the inner side of said tube,making contact with said concave pressure application face, is madelarger, and the wall thickness of the other, making contact with saidconvex pressure application face, is made smaller.
 7. A tube pump inaccordance with any one of claims 1 to 6, wherein the outside of saidtube is covered with a rubber tube.
 8. A tube pump in accordance withany one of claims 1 to 7, wherein a connection portion is formed at eachend of said tube so as to be integrated therewith.